I have a pair of skins for an old pair of...

You don't NEED them per se, but buying new skins means A. you don't need to replace any glue any time soon, B. you get a custom fit skin for your new skis with full(er) coverage that makes it easier for steeper ascents. If you want to just use them, you will be fine, and they will let you glide more on the flats.

yeah you will definitely have to get new skins for the Kantana's and when you do buy them get the width that is going to best cover your tip or tail, whichever is wider that's what is going to help you when you are skinning up.

if you are tight on cash, just put a slice the old skins lengthwise right down middle from about a foot in from each end. Then when you glue them on, just stick the edge of the skin along the edge of the ski. Voila DIY split skins